This invention relates to a heat-treating process and its apparatus in reducing air pressure within a chamber, which may attain very high efficiency with less heat loss.
The origin of this invention is based on Japanese Unexamined Patent Publication No. 57-144869 (Japanese Patent Application No. 56-29953 filed and invented by the present inventor), in which air within an airtight chamber is heated in reducing air pressure therein by means of suction means such as a vacuum pump and a heat source such as a heater. More specifically, by equilibrating a difference between the air pressure inside the chamber and a normal air pressure thereoutside while actuating an automatic valve, wet articles incorporated in the airtight chamber may be heated and dried effectively. Further, this prior technique may be applied for growing plants such as flowers, vegetables, fruits, etc.
In practice, by programming in advance the air pressure reducing condition, heating temperature and heating time in view of the kind, quantity, size and water-containing state of the articles to be treated, the heating operation most suitable for respective articles to be treated may be carried out in continuous drive. Accordingly, this process may be applied for various drying and heating purposes or for expediting growth of plants.
However, according to one aspect of this process, a thermal energy of hot air within the chamber is discharged wastefully thereoutside, while cold outer air is introduced into the chamber by way of an outer introducing pipe. As a result, when the hot air discharge function by the suction means and the cold outer air introducing function through the outer air introducing pipe are carried out simultaneously, the disadvantage of this process is that particularly in the winter season the temperature in the chamber is decreased rapidly, thereby the heating and drying operation becomes very inconvenient.
In particular, the wet articles such as medical plants, marine plants, flowers, etc. may be discolored or deteriorated in quality under the aforesaid heating and drying operation. Further, when expediting growth of plants, it becomes difficult to maintain the thermal energy in the chamber constantly. From this point of view, it is demanded to control the introduction of outer air accurately.
A further disadvantage of this process is that energy cost is incurred additionally due to energy loss.